Inflationary Theory and Alternative Cosmology

TL;DR

This paper critiques Hollands and Wald's claim that inflation doesn't solve cosmological problems, argues against their density perturbation mechanism, and emphasizes the necessity of early universe inflation.

Contribution

It refutes Hollands and Wald's arguments and defends the importance of inflationary stages in solving cosmological issues.

Findings

Hollands and Wald's critique is addressed and countered.

Their proposed density perturbation mechanism is shown to be problematic.

Inflationary stages are essential to explain observed large-scale structures.

Abstract

Recently Hollands and Wald argued that inflation does not solve any of the major cosmological problems. We explain why we disagree with their arguments. They also proposed a new speculative mechanism of generation of density perturbations. We show that in their scenario the inhomogeneities responsible for the large scale structure observed today were generated at an epoch when the energy density of the hot universe was 10^{95} times greater than the Planck density. The only way to avoid this problem is to assume that there was a stage of inflation in the early universe.